A conventional pin jack with a switch is explained with reference to FIG. 1 and FIG. 2A. Both movable contact 2 and fixed contact 3 are held within a body 1 made of insulation material. The body 1 is composed of a mounting part 4 and a contact housing part 5. The mounting part 4 is formed cylindrically, one end (the front end) of which has an aperture 6 for insertion of a plug pin. The other end of the mounting part 4 is integrally provided with the contact housing part 5. This contact housing part 5 is formed almost as a square box having a rear open surface. The movable contact 2 and the fixed contact 3 are inserted, from the open surface, into the contact housing part 5 and held therein. The mounting part 4 is covered with a metal sleeve 7. The front surface of the sleeve 7 is provided with an aperture 8 which is opposed to the aperture 6 of the mounting part 4 and is a little larger than it. The rear end of the sleeve 7 has an extended portion which is bent almost at a right angle and extended as a ground terminal 9. In FIG. 1, the sleeve 7 is indicated as being removed from the mounting part 4.
The movable contact 2 is composed of a movable piece 19 and a support body 11. The U-shaped support body 11 formed like a plate is inserted into the contact housing part 5 from the aperture at the rear side and both side edges thereof are inserted into grooves (not illustrated) formed in the internal side walls of the contact housing part 5. Thereby, the movable contact 2 is held and fixed. The movable piece 19 is extended toward the mounting part 4 as a spring leaf. The end portion of the movable piece 19 is formed like a tongue and curved toward the support body 11 as a plug receptor 12. The plug receptor 12 faces the rear end of the aperture 6 of the mounting part 4. The intermediate part of the movable piece 19 is integrally provided with protruding contact pieces 13a, 13b at both sides thereof.
The fixed contact 3 is formed as a U-shaped plate, and it is mounted opposite to the support body 11 of movable contact 2 within the contact housing part 5. The body side edges of the fixed contact 3 are inserted into grooves (not illustrated) formed in the internal side walls of the contact housing part 5. Thereby, said fixed contact is held and fixed to the contact housing part 5. U-shaped arm portions 14a, 14b of the fixed contact 3 are the fixed contact portions with which the contact pieces 13a, 13b of the movable contact 2 are in resilient contact. Moreover, the terminals 15, 16 are respectively bent almost at a right angle and extended from different side edges of the support body 11 of the movable contact 2 and the rear end of the fixed contact 3 and these terminals protrud to the outside of the contact housing part 5. The terminals 9, 15 and 16 all extend in the same direction.
As shown in FIG. 2 B, when a contact pin 18 of a plug 17 is inserted from the front side of the mounting part 4, the contact pin 18 engages the plug receptor 12 of the movable contact 2. With further insertion of the contact pin 18, the movable piece 19 of the movable contact 2 is resiliently displaced toward the support body 11. As a result, the contact pieces 13a, 13b are disengaged from the fixed contact portions 14a, 14b of the fixed contact 3 and electrical contact between the movable contact 2 and the fixed contact 3 is lost while electrical contact between the movable contact 2 and the contact pin 18 is attained. At the same time, a sleeve 170 of the plug 17 is engaged on the sleeve 7 of the jack.
In the conventional pin jack with a switch, the thickness of the movable contact 2 must be increased to achieve good electrical contact with sufficient contact pressure between the contact pin 18 and the movable contact 2 and to maintain the inserted condition of the plug. However, if it becomes too thick, particularly in case the movable piece 19 is short, the resiliency of the movable piece 19 is lessened, which allows only a small resilient displacement of the movable piece 19. Therefore, the displacement of the contact pieces 13a, 13b becomes small and the ON-OFF operations between the movable contact 2 and the fixed contact 3 can no longer be reliable. In order to assure the switch operation, the movable piece 19 must be sufficiently long to assure adequate resiliency of the movable contact. Accordingly, the jack becomes large in size. For these reasons, it has been difficult to simultaneously satisfy a good electrical contact function and reliable switch operation of the plug with a movable contact of the cut-and-raised spring type and to assemble a small size plug.